Desulfurizing mineral oil using an unsaturated nitrile with or without caustic



1956 A. SCHNEIDER ET AL 2,758,058

DESULFURIZING MINERAL OIL USING AN UNSATURATED NITRILE WITH OR WITHOUTCAUSTIC Filed April 26, 1954 igfiflg flfig caustic Treatment RefinedGasoline Caustic Soda caustic Soda I g 2 Caustic Soda Gasoline CausticTreatment Refined Gasoline Gasoline and wm m Caustic Treatment RefinedGasoline Caustic Soda 3 Caustic Sada Gasoline Caustic Treatment IRefined Gasoline Acrylonitrile Regeneration i INVENTORS. ABRAHAMSCHNEIDER y JAMES L. JEZL ATTO United States Application April 26, 1954,Serial No. 425,478 9 Claims. (Cl. 196-24) This invention relates to therefining of mineral oil, and more particularly to the reduction of theobjectionable mercaptan content of mineral oil fractions.

The mercaptan content of various mineral oil fractions presents adifiicult problem, particularly with regard to odor. Various means havebeen proposed previously for overcoming this problem, but none have beenentirely satisfactory. Ordinary caustic treatment of mineral oilfractions produces some reduction of objectionable mercaptan content,but the reduction is in many cases insufiicient to produce asatisfactory product.

According to the present invention, a mineral oil treating process isprovided which produces a highly satisfactory reduction in objectionablemercaptan content. The treatment according to the invention is capableof providing a greater reduction in objectionable mercaptan content thanprior art treatments, e. g. with caustic soda.

In the process of the present invention, mineral oil is contacted with atreating compound having the formula:

I II

where R, R, and R" are each selected from the group consisting ofhydrogen, methyl, and ethyl radicals. Examples of suitable suchcompounds are acrylonitrile, which is a preferred compound for useaccording to the invention, alpha-methyl acrynonitrile, betaethylacrylonitrile, betadimethyl acrylonitrile, alphamethyl-betadimethylacrylonitrile, etc. The amount of treating compound used is generallysmall, e. g. in the range from 0.001 to weight percent of the petroleummaterial treated, more preferably from 0.01 to 1 weight percent. In theevent that any excess of treating compound is used, the excess can ifdesired be removed from the petroleum material, e. g. by scrubbing thepetroleum material with water or an alkaline solution, or bydistillation of the treating compound from the petroleum material if thetreating compound is more volatile than all or part of the petroleummaterial.

The treatment according to the invention can be performed in thepresence or absence of an alkaline material such as ammonium, alkalimetal, or alkaline earth metal oxide, hydroxide or carbonate. Thetreatment may be at room temperature or at higher temperatures, e. g. upto 600 F. Preferably, if the temperature is below 200 F. the treatmentis performed in the presence of such oxide, hydroxide or carbonate.Preferred temperatures, when no alkaline material is employed, are 200F. to 600 F more preferably 300 F. to 500 F;

The treatment according to the invention is believed to involve chemicalreaction of the treating compound, e. g. acrylonitrile, withobjectionable constituents of the petroleum material,e. grmercaptans.The reaction product may, if desired be left in the oil, or if desiredit may be removed by suitable means, such as washing with water,treatment with adsorbent material such as clay, etc. In the case wherean alkaline material such as caustic soda is contacted with thepetroleum material, a part of the reaction product may be removed withthe alkaline material upon separation of the latter from the petroleumatent material. Hydrolysis of cyano groups in the reaction product tocarboxyl groups may take place, and the carboxyl-containing hydrolysisproduct may be removed in the form of a salt with the alkaline material.Such hydrolysis product can be precipitated from the alkaline materialby treatment with lime The treatment according to the invention isefiective to overcome the objectionable effects, not only of mercaptansin petroleum materials, but also of other nonhydrocarbon constituents ofpetroleum, e. g. hydrogen sulfide. The treatment of the invention mayadvantageously be applied to various petroleum materials such as naturalgas, refinery gases, dry gases, liquefied petroleum gases, gasoline,kerosene, spirits, gas oil, furnace oil, diesel fuel, jet fuel,lubricating oil, crude oil, etc.

The invention will be further described with reference to the attacheddrawing, wherein Figure 1 illustrates treat ment of gasoline with freshcaustic soda in the presence of acrylonitrile, Figure 2 illustratessimilar treatment with spentcaustic soda, and Figure 3 illustratesregeneration of spent caustic soda by contact with acrylonitrile.

In the process of Figure l, gasoline to which acrylonitrile has beenadded to form, for example, a 0.1 percent solution is contacted withagitation with caustic soda, e. g. five volumes of caustic per ofgasoline. The contacting can be conducted for example at ordinarytemperature without heating. At the end of the contacting step, themixture is allowed to settle, and the layers are separated. The refinedgasoline layer will be found to have been greatly improved in propertiessuch as mercaptan and H28 content, etc., the improvement beingsubstantially greather than that obtainable by similar caustic treatmentin the absence of acrylonitrile.

The gasoline treated as described above may have been given apreliminary treatment in the absence of treating compound according tothe invention. For example, it may have been treated with caustic soda,etc.

The process of Figure 1 illustrates improvement in caustic treating byuse of acrylonitrile. Acrylonitrile and other treating compoundsaccording to the invention can also be used to advantage in otherrefining operations; for example they can be added to various petroleumrefinery streams prior to distillation of the latter in order to providea beneficial refining action during the distillation.

In the process of Figure 2, one portion of gasoline is refined bycontact with caustic soda in the absence of a treating compoundaccording to the invention, and the spent caustic soda obtained uponseparation of layers is then contacted with a second portion ofgasoline, to which acrylonitrile has been added. The conditions oftreatment may be generally similar to those employed in the process ofFigure 1. The refined gasoline obtained by treatment with spent causticsoda in the presence of acrylonitrile will be found to be highlyimproved in properties, whereas a treatment with spent caustic soda inthe absence of acrylonitrile would be ineffective as a practical matter.

In the Figure 2 process, it is believed that the acrylonitrile probablyreacts with sodium mercaptides contained in the spent caustic soda toconvert those mercaptides into sodium hydroxide and non-objectionablecompounds containing mercaptan residues. The latter compounds may beextracted in part from the caustic by the gasoline in the second caustictreatment; if so, they are not objectionable in the gasoline, and theirremoval from the caustic soda leaves the latter in good condition forcontacting additional gasoline.

The spent caustic soda may contain sodium phenolates and/or sodiumnaphthenates, in addition to sodium mercaptides. The latter generallyreact more readily with acrylonitrile than do the phenolates andnaphthenates, and therefore spent caustic soda which has been con-2,758,058 3 i Y tacted a ylon'rile her eatmg compou ache atte use m1 ram at, preferably in the range cordin t the m e tion eneral] as Improvedsolvent rom 05 0 parts by we 'ght p r 100 parts f petropo er 80 11' raptld y lrflle of 1 'Hg leu Inaterral e p ferably from 1 to 1 part pereffect f phenolate ndnaphthen tes 100 Th ncentratzo he caustrc sod .i11gener- In h of Frgure 3 gasol e rs ontacted with 5 aly be in fro 5 5rcent th gh austrc d e ab ence of ylomtrrl nd the spent -1 rc cntranonsc be Us d, ustrc s (1 generated, a arati from t e re e re t mved the treatm cording t e 8011116 00 fact I b Ylonitr 1e Th r e 1 0beheved t be an ddrtr cross th generat n e effected by d e a rylonitzrleto d bl b treating t, 1 ca e of a the ga Ime t inary empera re W heating and 1 rnercaptan, S e S\ adical b1 ta es t0 agitatr the caustr totain act If deslred, one of h e carbg toms d elevate te peratures, up to200 higher can to h othe m c b tom. be emplo ed. enerally, e amo nlonitrrle o Th j v t I d other atlng c lpound e ployed W11 Within the 1.Metho r efining mineral 01'] W 1 range 00 10 par by We ht per parts of 5contactin inera] 01'1 coma caustzc so a, m preferabl 0.1 to 5 sperl Theaction Conditions 0 th as g mount of treat In on d may hosen uch that ji5 mg gxfg sodiu In rcaptd renr etc with the xl' "o l 3% g: ,1 53%?) 9 f:treatzng co pound p nolat naphthenar uqt us f l s'q in; I 2 p 00 nglargely nrea ted. e regen 10 g 0 ne oq 1 cfl c b used to onl'a tadd" glm1 v? 91! f e 1 n C materral, G ll gq 0? L G 2 Q t 11 0 11 2 Oh 916 I

1. METHOD FOR REFINING MINERAL OIL WHICH COMPRISES: CONTACTING MINERALOIL CONTAINING MERCAPTANS UNDER REACTION CONDITIONS WITH A COMPOUNDHAVING THE FORMULA: